Avoid FileMessageFactory leak.
FileMessageFactory will be removed immediately after receiving the complete WAR file but when failing to receive a FileMessage which was sent dividing, FileMessageFactory will leak without being removed.
Add a newly maxValidTime attribute to prevent the leak of FileMessageFactory.
FileMessageFactory that is leaking will be automatically removed after maxValidTime.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1479805 13f79535-47bb-0310-9956-ffa450edef68